Ultra high frequency harmonic generators or the like



Dec. 24, 1957 W. H. DOBBERTIN ULTRA HIGH FREQUENCY HARMONIC GENERATORS OR THE LIKE Filed Sept. 23, 1954 WILLARD DOBBERTIN INVENTORQ QWQM HIS ATTORNEY United States Patent ice ULTRA HIGH FREQUENCY HARMONIC GENERATORS OR THE LIKE Willard H. Dobbertin, Los Angeles, Calif., assignor to Hoffman Electronics Corporation Application September 23, 1954, Serial No. 457,835

3 Claims. (Cl. 250-36) This invention is related to ultra high frequency harmonic generators, and more particularly. to an improved ultra high frequency harmonic generator which is relatively inexpensive to manufacture, and which also exhibits optimum performance at all operating frequencies.

In the past, many designs have been proffered regarding ultra high frequency harmonic generators. Invariably, such harmonic generators utilize klystrons or other ultra high frequency vacuum tubes, and also employ rather involved circuitry.

Therefore, it is an object of, this invention to provide an improved ultra high frequency harmonic generator which will be relatively inexpensive to manufacture.

It is a further object of this invention to provide an ultra high frequency harmonic generator which will lend itself to reliability, minimum radiation, and optimum perform ance over the entire frequency range in use.

According to this invention, a signal distorting crystal diode input is coupled to a resonant cavity construction capable of being tuned to select particular harmonic in the distorted input wave form of an input signal when this signal is translated through the aforementioned crystal diode. The resonant cavity construction consists of a cavity and a center resonant line which may be capacitively loaded by means of a probe which is capacitively coupled to an adjustable end portion of the aforementioned cavity. One or more inductive probes within the cavity couple the selected harmonic signal to an associated output terminal.

The features of the present invention which are believed to be novel are set forth with particularity in the appended claims. The present invention, both as to its organization and manner of operation, together with further objects and advantages thereof, may best be understood by reference to the following description, taken in connection with the accompanying drawing, in which the sole figure is an elevational perspective view of an ultra high frequency harmonic generator, according to the present invention.

In the sole figure, harmonic generator is shown to consist of cap assembly 11 and cavity resonator assembly 12. Cap 13 of cap assembly 11 is internally threaded. Adjusting screw 14 is threaded into a tapped hole in cap 13. Locking nut 15 is provided to lock adjusting screw 14 in a chosen vertical position. Cylindrical cavity 16 has externally threaded end portion 17 and output attachment flanges 18. Cylindrical cavity 16 is closed at the lower end by base element 19. Base element 19 may, of course, be manufactured integrally with cylindrical cavity 16. Resonator 20 consists of resonant line portion 21 and capacitive probe portion 22. Resonator 20 is affixed to base element 19 in conventional manner. Resonant line portion 21 of resonator 20 has provided on its periphery a receptacle portion 23 to receive one terminal of crystal diode 24. In addition, access hole in the wall of cylindrical cavity 16 is provided to accommodate the placement of crystal diode 24. The remaining terminal of crystal diode 24 is to be connected to external signal generating circuitry (not shown). Atlixed by screws or other 2,817,760 Patented Dec. 24, 1957 means to output attachment flanges 18 of cylindrical cavity 16 are two output terminal receptacle assemblies 26. Receptacle assemblies 26 each consist of mounting fiange 27, cylindrical L-section element 28, insulator 29, probe 30, and output terminal 31. Inductance probes 30 are each grounded at one end and are of appropriate length and spacing from resonant line portion 21. Of course, any number of output terminals may be employed using substantially the same configuration shown in the sole figure. Input receptacle 32 is shown disattached from its respective mounting flange, for sake of clarity.

The harmonic generator apparatus shown in the sole figure operates as follows. A high frequency signal source (not shown) is coupled through crystal diode 24 to harmonic generator 10. Crystal diode 24 will pass either the positive half-cycles or the negative half-cycles of the input signal, depending upon which end-terminal of crystal diode 24 is disposed within receptacle 23. The properties of crystal diodes are such as to distort the wave form of the signal passing through them. Hence, a distorted input signal will be fed to resonant line portion 21 of resonator 20, of the harmonic generator. The positioning of receptacle 23 upon resonant line portion 21 will be dictated by a maximum energy transfer for a given cavity load. If it is considered, for the moment, that cap assembly 11 and capacitive probe portion 22 of resonator 20 are eliminated from the harmonic generator configuration, then the overall height of cylindrical cavity 16 would have to be approximately 7.5 centimeters, i. e., one-fourth wave length at a frequency of 1,000 megacycles, for example. Or, considering resonant line portion 21 to be a quarter wave length resonant line, the length thereof at 1,000 megacycles must be 7.5 centimeters. The present invention allows the quarter wave resonant line section to be shortened physically by end-loading capacitively. This capacitive loading is accomplished by varying the capacitance between capacitive probe portion 22 of resonator 20 and the top portion of cap assembly 11. It is to be noted that the downward progression of cap 11 uniformly reduces the height of the cavity without distorting the cavity and incurring mode skipping which might otherwise occur by such distortion.

As is well known in the art, the subject configuration may be thought of either as a re-entrant cavity resonator or as a coaxial transmission line short-circuited at one end and in quarter-wave resonance. As the length of resonant line portion 21 is decreased, the apparatus will progressively exhibit resonant cavity characteristics. It will be true that as the distance between capacitive probe portion 22 and cap 13 of cap assembly 11 is increased, the capacitance loading will decrease and the consequent resonant frequency will increase, and, simultaneously, the effective electrical length of the cavity will increase, thereby reducing the resonant frequency and tending to cancel the decrease in capacitance loading. However, the latter effect will be very small in comparison to the effect of changing capacitance, owing to the relative proximity of capacitive probe portion 22 with respect to cap assembly 11. Therefore, the subject invention provides a way for tuning the cavity resonator to a particular harmonic of the fundamental frequency of the signal source, and selecting the same for transmission to output terminals 31. The design of inductance probes 30 and terminal receptacles 26 may be such as to match the impedance of a conventional 50 ohm coupling line.

It is seen that this invention provides a relatively simple and inexpensive apparatus for generating and selecting harmonies of any particular fundamental frequency and feeding such selective harmonic to any and all of the output terminals employed.

While particular embodiments of the present invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from this invention in its broader aspects, and, therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of this invention.

I claim:

1. An ultra high frequency harmonic generator including, in combination, a signal input terminal; a crystal diode having first and second end terminals, said first end terminal of said crystal diode being connected to said input terminal; a resonator element having a resonant line portion and a capacitive probe portion, said resonant line portion of said resonator element having a terminal receptacle adapted to receive said second end terminal of said crystal diode; a cylindrical cavity enclosing said resonator element and having means for receiving and securing output coaxial connectors, a threaded end portion, and a base portion to which said resonator element is aflixed; a threaded cap element in capacitive relationship with said probe portion and adapted to cooperate with said threaded end portion of said cylindrical cavity; and at least one coaxial output connector mounted upon said securing means of said cylindrical cavity and having inductive probes grounded at one end and disposed within said cylindrical cavity adjacent said resonator element.

2. Apparatus according to claim 1 in which the disposition of said terminal receptacle of said resonator element is uniquely positioned upon said resonant line portion to provide a maximum transfer of energy.

3. An ultra high frequency harmonic generator including, in combination, a signal input terminal; a crystal diode having first and second end terminals, said first end terminal of said crystal diode being connected to said input terminal; a resonator element having a resonant line portion and a capacitive probe portion, said resonant line portion of said resonator element having a terminal receptacle adapted to receive said second end terminal of said crystal diode; a cylindrical cavity enclosing said resonator element and having means for receiving and securing output coaxial connectors, a threaded end portion, and a base portion to which said resonator element is affixed; a threaded cap element in capacitive relationship with said probe portion and adapted to cooperate with said threaded end portion of said cylindrical cavity, said cap element being provided with a positioning screw and locking nut which are positioned and adapted for cooperation with the end of said cylindrical cavity; and at least one coaxial output connector mounted upon said securing means of said cylindrical cavity and having inductive probes grounded at one end and disposed within said cylindrical cavity adjacent said resonator element.

References Cited in the file of this patent UNITED STATES PATENTS 2,177,272 Zottu Oct. 24, 1939 2,408,420 Ginzton Oct. 1, 1946 2,566,759 Clark et a1 Sept. 4, 1951 2,600,278 Smullin June 10, 1952 2,605,399 Pound July 29, 1952 2,616,037 Wheeler et al Oct. 28, 1952 OTHER REFERENCES Article: Harmonic Generation Diodes, pages 68 of General Radio Experimenter; vol. 26, No. 2 for July 1951. 

